Nowadays, converter circuits are used in a wide range of power-electronic applications. A converter circuit such as this should firstly produce as few harmonics as possible on phases of an electrical AC voltage power supply system which is connected to the converter circuit, and on the other hand transmit power levels that are as high as possible with as small a number of electronic components as possible. One suitable converter circuit for switching a multiplicity of switching voltage levels is specified in DE 692 05 413 T2. This document specifies a switchgear cell having a group of connection, with the group of connection having a first and a second controllable bidirectional power semiconductor switch and a capacitor. The first and the second controllable bidirectional power semiconductor switch are each formed by a bipolar transistor with a drive electrode arranged in an insulated manner (IGBT—Insulated Gate Bipolar Transistor) and by a diode connected back-to-back in parallel with the bipolar transistor.
A switchgear cell for the converter circuit for switching a multiplicity of switching voltage levels according to DE 692 05 413 T2 stores electrical energy in the switchgear cell during operation that is very high. Since the electrical energy is stored in the capacitor in the switchgear cell, the capacitor and the power semiconductor switches are designed for this electrical energy, that is to say with regard to the withstand voltage (blocking voltage) and/or the capacitance. However, this involves capacitors with a large physical size, which are correspondingly expensive. Furthermore, the switchgear cell and therefore the converter circuit as well use a large amount of space because of the physically large capacitors, so that a space-saving design, as is desired for many applications, for example for traction applications, is inhibited. Furthermore, expensive and complex power semiconductor switches are used which have a high withstand voltage. In addition, the use of the physically large capacitors can result in a large amount of assembly and maintenance effort. In addition, the converter circuit for switching a multiplicity of switching voltage levels according to DE 692 05 413 T2 can be susceptible to high voltages, in particular to over voltages, because of the exclusive use of bipolar transistors with a control electrode arranged in an insulated manner as the controllable power semiconductor switch, and can also produce considerable power losses.